To meet the demand for wireless data traffic having increased since deployment of 4G communication systems, efforts have been made to develop an improved 5G or pre-5G communication system. Therefore, the 5G or pre-5G communication system is also called a “beyond 4G network” or a “post LTE system.”
The 5G communication system is considered to be implemented in higher frequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higher data rates. To decrease propagation loss of the radio waves and increase the transmission distance, the beamforming, massive multiple-input multiple-output (MIMO), full dimensional MIMO (FD-MIMO), array antenna, an analog beam forming, large scale antenna techniques are discussed in 5G communication systems.
In addition, in 5G communication systems, development for system network improvement is under way based on advanced small cells, cloud radio access networks (RANs), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, moving network, cooperative communication, coordinated multi-points (CoMP), reception-end interference cancellation and the like.
In the 5G system, hybrid FSK and QAM modulation (FQAM) and sliding window superposition coding (SWSC) as an advanced coding modulation (ACM), and filter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) as an advanced access technology have been developed.
Meanwhile, the 5G communication system has considered a support for various services compared to the existing 4G system. For example, the most representative services are an enhanced mobile broadband (eMBB) communication service, an ultra-reliable and low latency communication (URLLC) service, a massive machine type communication (mMTC) service, an evolved multimedia broadcast/multicast service (eMBMS), etc.
Unlike the existing 4G system, the URLLC service is a service that is newly considered in the 5G system and need to satisfy ultra high reliability (packet error rate of 10−5) and low latency (0.5 msec) conditions, compared to other services. For example, the URLLC service may be used for services such as self-driving, e-health, and drone.
However, a scheduling request procedure which is basically performed in a cellular uplink system requires a plurality of information exchange processes between a base station and a terminal and therefore is not suitable to achieve the low latency target of the URLLC. Therefore, a grant-free and contention-based transmission technique is considered for supporting a URLLC service in an uplink system.
In addition, an mMTC service considers the minimization of the power consumption of the terminal as a very important performance index. To this end, the terminal needs to minimize a control signal exchange with the base station. However, the uplink scheduling request procedure is not suitable to minimize the power consumption of the mMTC because the uplink scheduling request procedure requires a plurality of information exchange processes between the base station and the terminal. Therefore, the grant-free and contention-based transmission technique is considered as a main scenario to support the uplink mMTC.
Meanwhile, in the uplink cellular network, the terminal can be operated based on downlink synchronization acquisition information. However, since the uplink system transmits a signal to one base station at terminals located at various positions, a receiver (base station) receives signals at different timings even if the downlink synchronization is obtained. Accordingly, the cellular system can estimate an arrival time of a received signal from each terminal in advance and transmit the signal to the terminal in consideration of the corresponding time, which is referred to as timing advance (TA) value compensation. In general, the TA value can be calculated based on initial random access channel (RACH) processing and updated based on a periodic RACH re-execution procedure.
However, when supporting the uplink mMTC or URLLC, the RACH procedure may not be performed again to minimize the information exchange process between the base station and the terminal. Therefore, the TA value estimated based on the initial RACH procedure is different from the TA value of the uplink transmission time of the actual terminal, which may cause a timing offset in the receiver (base station) to significantly reduce error probability performance. Therefore, there is a need for a method capable of preventing deterioration in performance due to an occurrence of a timing offset.